if we select country in dropdownlist(like india) and then next dropdownlist show state ( like delhi) show in dropdownlist in asp.net

       if(!ispostback)
       {
              FillDropDownList();
       }
    

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 private void FillDropDownList()
    {
        DataSet ds = new DataSet();
        SqlDataAdapter myda = new SqlDataAdapter("select Country from table name",connection object);
        myda.Fill(ds);
        drop_country.DataSource = ds;
        drop_country.DataValueField = "Country";
        drop_country.DataBind();
    }

protected void drop_country_SelectedIndexChanged(object sender, EventArgs e)
{
    DataSet ds = new DataSet();
        SqlDataAdapter myda = new SqlDataAdapter("select state from table name where country='"+Drop_contry.Selecteditem.Value+"'",connection object);
        myda.Fill(ds);
        drop_state.DataSource = ds;
        drop_state.DataValueField = "state";
        drop_state.DataBind();
}